Learned Associations and Human Attraction

Welcome to the Rest of Science, I'm Hanah Fry, and I'm Mael Stevens. Here's a question for you, Michael. What is going on with feet With my feet? Yeahah ost yours, but also yours. Okay. no one knows what's going on with my feet because I never show them off. Do you know? Okay, I guess I did once when I stepped on LegOos like for a bit to get views, but when I was a small child, like a child I had hairy feet. Yes. And I was walking around barefoot one day and my dad's friend whose name was Al. Like, I'm not afraid to name and shame He looked at me and he goes to my dad and he goes Whoa, your son's feet have a lot of hair on them Wait, how old were you at this point? Okay, in my mind, I'm like four, but I'm sure I'm sure I was like a teenager. Are we talking about like sort of soft downy children hair or are we talking about like no, we're talking about hair. Like look at my beard And then imagine toes coming out of it It's it's almost like that Even at home, I've been married to my wife for ten years now. I still just wear socks all the time so she won't go Whenever she sees me. A they still harry Will you haven' shaved him Wow. This episode is not about me. Okay This episode is about our entire species. It is about our entireies. I hadn't really thought about it until you mentioned it, but they are a bit weird. They are very weird. They're very different to other animals And that iss what we're going to get into it. Listeners Don't worry. We're gonna come back to Michael's feet as well, because I've got more questions. I've got more questions. I have no more answers Or do I This episode is brought to you by Cancer Research UK. Scientists have found that cancer risks usually increase with age and size, but some species defy the odds. For example, deep sea Greenland sharks. They can grow over six meters long. way more than a small car and yet live for up to four hundred years. Now understanding how Green and sharks cellular repair and immune systems seem to have managed to keep them cancer free for centuries, that could open up exciting research pathways. Essentially over millions of years, evolution has been running the world's most successful cancer prevention trial. And sometimes breakthroughs can be found in unusual places So by exploring the unexpected, cancer Research UK scientists are uncovering new ways to tackle over two hundred types of cancer. Their work has helped to double survival in the UK over the last fifty years and continues to save and improve lives around the world. For more information about Cancer Research UK their research and breakthroughs and how you can support them Visit cancerreesearch UK dot org slash the rest is signed Queen Carvania stood haloed by the morning sun. army hung on her every word. 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Let's talk about a condition many people haven't heard of. turns out, it's more common than you'd think Pyrony's disisease, or PD for short PD can happen when scar tissue builds up under the skin of the penis This can cause a curve or a bump during an erection and for some men, lead to pain during intimacy and may impact mental health It may also lead to anger and frustration deression, lower self esteem and even withdraw from sexual activity and physical intimacy Because of this, some men could feel embarrassed or reluctant to talk about PD The actual cause of PD isn't always known In some cases, it may be linked to a minor injury or repeated injuries during sex or other physical activity The good news is PD is treatable If you notice a curve with a bump, A trusted Uurology specialist can help diagnose it and walk you through your options, including non surgical treatment To learn more about Pyron's disease, visit talkaboutpD d. com. So I was in Cambridge the other day having lunch and I ended up chatting to a colleague of mine called Sreus Mandre He raised this question with me. I'm like, Why are human feet so weird compared to every other creature that exists, okay? If you think about it The same solution has evolved over and over again in the form of hooves and trotters. What's a trotter? A trotter? It like a paw? It's like it's on a pig, you know? Oh, okay. It's got a split. It's of likeiff differentere than a hoof. Pigs don't have hooves, do they? It's sort of halfway between, it's slightly softer than a hoof. See, I'm not afraid to admit what I don't know But know, I'm also now worried about the limits of my own knowledge of Totter vers. Hoof. Is anyone Jewish here becausecause they would know. They've got that whole rule about You can't eat a hooed animal unless it chews cud Really? Yeah Do you know what? I think Trotter might be a kitchen word Bea if you look atotter pigs trrotter on Wikipedia, it's a culinary dish And the picture is pretty. Gim Grim Like it's good. It illustrates trotter. That's what you need. It does not look appetized. It does not. It does look quite undignified I would not want to be that pig, put it that way. Okay, but his holdold on. If you're gonna be a pig who's going to be slaughtered, you could do worse than being the pig whoses trotter gets pictured on Wikipedia for eternity. You're immortalized. I don't think I would care that much about legacy as a. Oh I would. I'm like, I'm in it, I'm in it for For the legacy, for the fame. Yeah Yeah, for the photos. The immortality of my trotter, A little trotter, my little trotter's Okay, here's the thing, right? Hooves make really good mechanical sense, you know've got you want to be a fast heavy runner, you evolve hooves, right? you're not damaging the ground. If you want to sprint and hunt, then you evolve paws. They're much softer. they're like squishy jelly bean pads. If you want to climb, then you evolve a kind of second pair of hands, which is what you get with monkeys Human feate, what is going on with them? Right? it's kind of halfway between climbing and not climbing. Right. grasp, but monkeys have much more opposable They do. In fact, my daughter has a book about human evolution, and it's got all these artist renderings of early hominids and they all have like hand feet So yeah, what not only Is that different, but also Homo sapiens are the only animals on this planet that wear shoes. Right. Now we put them on horses. Sure. When they're doing labor for us, we'll put them on dogs, but only when the dog is gonna be walking on something we made like asphalt or concrete. By the way, do you say asphalt or ashphalt? Asphalt. I say felt. I dont know. It doesn't come up that often. It doesn't in my world, I'll be honest Anyway. And so why what's going on there? right They are weird. They are weird. They are weird, but I think the shape of them in particular, when people first started trying to make robots, okay, the first time that you sort of needed to like construct a foot to see how it could work And they tried to make these like flat feet. It's just like kind of moving this, right? whichich is maybe that's how our feet have evolved. Maybe it was that we were previously climbing trees and then they just became slightly flatter, slightly less able to grip around the trunk of a tree and slightly more attuned to going on the groundet So when people first started building robots, they made these perfectly flat feet. and it was a total disaster Because what that means is if your feet are completely flat, you can't roll forwards. Right. So instead, like the early robots like Azimo, which is a particularly famous one, they have to if you look at them, they have to stand essentially with their knees permanently bent in order to be able to move forward. right? It's really, really energy intensive to lift your feet up this way And if you look at an ape walking, that's essentially what they're having to do. Oh really? Because their feet are so flexible, right that when they are down on the ground, boof, they have them very flat. And so their knees and their hips are continually having to be bent in order for them to propel themselves for. It's like really energy intensive. if they don't like doing it at all would much rather be in the trreace. And so a firmer that's less flexible like a human foot is better for walking. Right. You sort of want the rigidity in order to be able to kind of press off, but you also don't want it to be flat Right Because the flat obviously takes a lot of energy needs to be somewhere in between. Yeah. But then here's a question, okay? You don't want it to be flat, you want it to be rigid Why isn't it shaped like a rocking chair? That would help you prepel for work? Oh, yeah I mean that would make way more s I mean it needs to be I need to be able to move it. L I need my toes to be able to sometimes give more or less resistance to the. mot aggreed, but like this kind of this effect of like rolling forwards, and yet our feet are arched exactly the opposite way. They are, aren't they? Yeah. So this was a genuine puzzle. Why is it that our feet are arched that way r rather than the other one? Can I make a guess or I would guess that it's like architectural for support that that arch Just like an arch in architecture holds weight better than like a saggy Rcking chair type I don't think that's the primary. So what other reason is there? It's probably because standing still would be really difficult. If our feet were bent like a rocking chair. people have tried this with robots as well. Right. So the sort of next generation of robots had rocking chair type feet But then standing still would require you to continually tate yourself. You'd have to like permanently be locked in place. Yeah And so it just doesn't work either So instead with the arch the other way, it means that you can kind of create a triangle between the big toe sort of pinky side of the four and your heel and you're kind of sitting on a little tripod So your tripods. Yeah kind of being in a relaxed state But in the nineteen fifties, people were like, this does still really not make a lot of sense. Like why have we got this? Maybe the foot arch is there for structure, but you know it makes sense why we add these flat feet. but what is going on? Like why are our feet in this particular shape So in the nineteen fifties this English orthopedic surgeon, he was like, G, I've cracked this. I've worked it out. He was kind of looking at the human foot And he knew it couldn't be a rocking chair, but he also knew that if it was just this fly floppy bag of joints, you know, this insane number of bones. Like a monkey foot. Like a monkey fooot, then we wouldn't be able to push off. and it would be really, really difficult. So he was like, right, there must be this kind of structure that's going on in here This is the explanation that he managed to come up with, okay? Oh You've got a cardboard model. I did you built it yourself. I did in the car on the way here. It's got like an arch. it's like a cardboard shaped boomerang. Yeah, it's got three different parts to it, okay? So those of you who are watching, you can see this is sort of like learen with Hannah. Yeah this is my model of the foot and how foot works, or how they thought the foot worked in the nineteen fifties. Okay, so so let me say what I'm seeing. G. Th parts. One looks like a boomerang shape. Yeah. And then attached to one end is a little ellipse that is hinged like like with a Bad. So it can swirl around three hundred and sixty. Yeah said, I mean, that's that's not what you want in your own ph It's not what you want and I can tell that because you've connected Fom the far end of the boomerang to the far end of the ellipse with a rubber band. So it's almost like a bow and arrow type. Exactly. It's like a bow and arrow tyight shape exactly. So what you can't quite see here, I've essentially split the foot into three sections and then we have like a tendon running between hu. So here is the heel, It's kind of the back of the foot. and then you have essentially the foot arch that goes up and over And then this here is the toes, okay? Right. So now the ellipse is the toes. The ellipse that can move around is the toes. it hinges there. So here it was his idea. He was like, the foot being this shape, like a bow from a bow and. Yeah. This makes perfect sense. becausecause when you put your foot down, You've got lots of nice kind of elasticity so your foot doesn't get damaged. The kind of the string from the bow hits the ground first and absorbs lots of the energy as you hit the ground But if you move forward by lifting your heel up, then what you're doing is you're tightening this bow, you're tightening the tension between your heel and your toe. and that's the thing that's giving your foot this structure. That's the thing that's giving your foot this strength, this stiffness in order for you to be able to push off and move forwards, right? It's something that just made absolute perfect sense As a result of this explanation, this explanation, by the way, stood for like seventy years. Everyone was like super happy with it And it led to something called Jack's test, which you can do it on yourself There was a bit of me Michel that was going to suggest that you get your feet up for this, but maybe not. May Maybe later. Maybe later. But if you stand bare first, it's for the rest is science after dark. Yeah, that's the subscription. Yes, yes. You know, I think Lily Allen once said she's got O fans, but she only shows pictures of her feet. Okay. And she said that she makes more money from that than she does from her actual music. I believe her. That's incredible. is. Yeah. Well, she probably doesn't have like Ticket master fees and a recording label to pay. Very true. She just snaps them with her phone K Ching, King hello I'm going to come on too that a bit more later, the foot fetter stuff. It wouldn't be a proper episode about feet if I didn't ment No, we have to. we have to, we have to Okay, so so there's this thing called Jack's test If you stand barefoot with your weight on the floor and you have somebody else pull your big toe backwards. So you're kind of standing like this And then you get someone else to effectively tighten. So simist st up. They pull your big toe up. Then you will see At Basically. you see your arch kind of getting tighter more stiff, essentially Everyone was like, well, this is the proof that his explanation is correct. It's very clear that moving the big toe moves this tendon, the plantar fascia that runs between the front and back of your foot. And everyone was like, well there you go, this is it. We worked out. This is absolutely fine And then what would happen is this kind of like really fed into the medical understanding of what it meant for feet to be working correctly. So you might have heard this idea of people saying, You're very flat footed.. And that being considered a real problem. Right. And it comes from this exact same explanation that if your foot is too flat, if your arch is too narrow, then you can't get the tension properly and it affects the way that you end up walking There was some confirmation bias going on in this too, because people would go to doctors and they would say, We've got loads of pain in our feet And the doctors would look at their feet and say, what' ' becausecause your feet are flat? I can see that there's a flattenness to your foot and that must end up being the problem. Okay The slight issue right with this explanation? Well there's two. The first is If this really is the way that feet work Well, then how come people who do have completely flat feet and walk Yeah, they can. They can It is possible.t need you don't actually need the ar. Well, I remember being told as a kid that I had flat feet by my doctor. But I didn't know what the symptoms were supposed to be. Right. I could walk fine. I could run fine. It's never been a problem. What did they what did they say about it? I don't remember anything outside of he made me walk around barefoot in the Doctor's office Maybe you just wanted a free sweeping of his floor. Maybe that hairy Mbe you thought your feet were so flat because he couldn't see through all the hairs. C couldn't see through all the hairs at this forest. No, I remember him telling my mom, yeah, he's kind of got flat feet, but then nothing ever came of it. so Right. And it doesn't matter at all because Be while some people who have pain in their feet have flatter feet than others There are also like loads of people who've got incredibly flat feet and like run marathons and do all this stuff and they're absolutely fine. Like they're completely fine. That what I was thinking, Yeah. And then there are plenty of people with really nice arches who have absolutely completely. The other big clue that this explanation was completely wrong is that for this explanation to work the way that they constructed it is that you sort of have to fuse the heel and the arch, kind of this particular joint is like quite rigid in the explanation. But then it turns out that there have been some surgeries where people who've got really bad arthritis have had that joint physically fused makes it really, really difficult to walk So how can it be? And this is the joint between The heel and the rest of your Let me get the. I't know there was even a joint there.' I mean, there's lots of joints. I think there's thirty joints in the foot in total. Oh goodness. I mean, this is sort of pretending that there's two. There's Yeah, right. but yeah, there's It's called the navicular medial cuneiform joint. Okay. Okay. and if you fuse it the existing idea of how feet work, not a problem at all in reality makes somebody's ability to walk significantly worse. So it's like, Well, this is like there's something wrong going. something something is wrong going on here. Very recently In twenty twenty paper that my colleague at Cambridge was involved in a group of scientists, mechanical engineers and biologists essentially Well, like something is going on something not right So they decided to look at the foot from a completely different angle Because this entire time when we've been thinking about the mechanics of a fur We'd been looking at the arch that runs from the toes to the heel. Yeah this group were like, well, hang on a second There is another arch going on in your foot. Your foot doesn't just bend front to back, it also bends left to right Like if you think about the way that you have a pringle, like a pringle, Exactly You're looking at your feet now. Yeah, I know, but I've got shoes on. so I'm like, No, it's pretty darn flat. But yeah, I know you're ding your combor c underneath. Yeah, exactly. And actually they were like, well hang on a second. Mbe it's maybe the stiffness becausecause you need your foot needs to have this stiffness in order for you to be able to push off and prepare yourself for it So they were like, maybe the stiffness is coming from the arch that runs in the other direction instead. Rather than front to back, maybe that one's not as important. maybe it's side to side, from the big toe to the pinky toe So what they did G got Horeson cadaffy. Greaceon Keep going. They mounted these feet into this like quite heavy duty materials testing machine they would like Press. weight's down on the thm to see how much force it would take to bend the midferm. And these were cadaver feet that were not compensating for the extra weight. They were just looking at the structural properties. structural properties f nothing else. And then once they'd done that, they then got out some scissors and they started snipping the joints between the toes. Right Not just between the toes but in that direction, right? Trying to break the arch that runs when it fails. And it turns out that this like you know really decades and decades and decades old understanding of the ft just hold as the snips took place Because almost all of the rigid structure of the foot comes from the left to right arch, not the front to back up. Wow. like completely shattered this biomechanical dogma that existed Yeah, when they ran the numbers, the front to back arch only accounts for about twenty five percent of the foot's rigidity. Okay. Now the reason why this works, the reason why you get this stiffness something called Gaussian curvature. The reason why you get stiffness from there being a bend It's a bit like you know, when you have a slice of pizza Y So a slice of pizza, if you try and get it in your mouth, I'm doing this with a piece of paper. It wouldd be much more fun if it was an actual pizza. but I'm imagining. You're imagining, o. If you have a slice of pizza and you try and get it into your face. Right. You're holding it from like the crust end So the tip is gonna to flop down. It flops down really easily. Yeah. But what people automatically do is they realize that if you fold it along the length of the pizza Then when you try and get it in your mouth, it remains straight in the other direction. I've seen the famous like Ted Ed animation about this pizzizza why pizza folding makes things rigid, but you're saying that this is also what makes our feet rigid and great for walking. Yes. so it all comes down. comes down to this idea of gausing curvature. so gaussing curvature is something that measures the curviness of a surface And it's made up of two numbers. So one number is how cururvy it is in one direction The other number is how curve it is in a perpendicular direction. perpendicular direction. Exactly. So if you imagine that you're on the surface of a globe, right? say you're at the equator One number would be north to south, how curvey is in that direction and the other would be east to west Now the key thing, it's positive if it curves away from you. Okay Okay. Now the key thing about gazing curvature, is that you cannot change the gaussian curvature of a surface unless you cut it or warp it. Right. So if you start off with something that is completely flat, you know like a piece of paper or a piece of pizza If you start off with something that is completely flat, it has zero Gaussian curage. Yeah whichich means that even when you bend it, it has to end up with zero Gaussian curvature.. So when you bend a sheet of paper, you produce, say positive curvature in one direction one axis. Yeah. Now the only way those two numbers multiplied together can still make zero is if the other direction is zero. Right? You've forced it to have a positive number in one direction Yeah positive number times zero is still zero. So you have forced it to have zero curvature in the other direction. The curvature of a flat sheet of paper is zero. zero times zero in all zero times zero. Yeah So it's the product that matters. Yeah. So if you crereate a curvature of, say one, I don't know what the units are, but positive one. That means you're like turning your page into a taco. The curvature in the perpendicular direction. Nes to be zero because one time zero is still zero. Exactly Exactly. So this is why the folding pizza thing works. Yeah. You force it to have a positive curvature in one direction, which means the law of light curvature has to not have curvature. Sure The only way it could have a different curvature in the perpendicular direction now is if it warped or broke. Exactly. Which is strong enough not to. Exactly. It's the same reason why corrugated cardboard works because you take the paper. I mean, it's actually quite thin, corrugated cardboard, right You take it and you curve it, you deliberately give it a curveat during one direction, which means that it then can't bend in the otherirect other. Right. So it's the same with your foot. You deliberately curve it in one direction between your little toe and your your big toe. And it means that then it cannot curve in the other direction, which means that it has this stiffness as you propelled yourself forward I want to take a quick tangent and talk about globes. Yeah because the Eth is going to have positive curvature to the same degree in both East West and North south direction. That's one of those axes So it's curvature if we call it one in each direction is one, onene times one. What could I do to a globe such that the product of those two curvatures is still one? So So actually, with the globe, this is the reason why maps don't work Yeah because I' to, I'm changing its Gausian curvature from one to zero zero and so it doesn't work. I'll get ripped without you ripping it, cutting it, or warping it. Are there other shapes I can bend it in into that still have a Gaussian curvature of one? Yes, Not a cylinder because that's got a gaussian curvature zero. becauseuse it's beennd in one direction, but not in the other Not a pringle because that has got positive in one direction and negative in the other It's still going to be positive, positive. because that's the only way that you get a positive number overall. So you're looking at like Blates fheroids, rightight, you know sort of like deformed balloons. That's essentially all you got All right, but you know Let's save this for the globe episod. Let's see what kind of crazy deformed balloons we can make And crazy deformed maps. And crazy deformed maps. Yeah. Yeah ack to the foot though, pase. This is like, okay, so so maybe this is what was going on all this time And it has since been confirmed. They've done high speed x rays of what is going on with a foot So where you can take a x ray as somebody is walking or moving theirot sort of move away from the cadapphy at this point watch a runner essentially move around while having x rays. a slow motion X ray? I would love to wash them. No. A actuallyually, in fact, I think I have some. How did they get volunteers for that? X ray videos are amazing. Like I've seen X ray video of people swallowing and chewing. Of course, it's a carcinogen, all these x rays being shot at you. so it's not a good idea. They used to, of course have actual X ray boxes at shoe stores. Yeah. You could put a shoe on your foot and then stick your foot in the box and look through this window and see the bones of your foot and how they were being squished or not by the shoe. Yeah. Not a good idea. That was a bad idea. But they were helpful Theyay you didn't want to live a long time and have comfy feet. If you wanted comfy feet, if you wanted the next few years to be really comfortable, they were great. I think you can think of everything on a spectrum, right? between how much do you care about comfy feet versus how much do you care about wanting to live, right? And in the limit If my feet were excruciating all the time, I'd be fine with a shorter life, you know? So this is just exactly, it all balances out. It all balances out. all balances out Yeah, when you do these x rays, it's like the foot is this spring loaded trampoline essentially. You're just the second before your toes leave the ground, the arch just visibly recoils, it kind of springs back into its curve shape And that elastic bounce releases all of that stor and energy thr throwing the body forward. mooving you forward. Moving you forward. yeow Cool. Yeahah. I really like that a lot. They ends up going further because they were sort of, o, well if it is about this way round rather than that way round. When you go back in the fossil record It was before this paper came out about the direction that we know that it matters in There was a bit of a question about this because some of our ancestors, Lucy, for example, the one that was found three point two million years ago, right has like these very flat feet. Flat in the direction of toe to heel. Flat in the direction of toe to heel, but not flat in the direction of bigig toe to littleittle toe. Okay, so is that evidence that she was a walker? It's evidence y had a walker. Yes, that it was like this she was essentially transitional. She was somewhere between climbing trees and walking upright. So then what's the point of the curvature from toe to heel? So that still helps with the it's a quarter of support. a qu Yeah It's just not providing the stiffness. Right. It's helping you propel forward. It's part of the kind of trampoline like ing loading, it's just not the thing that's giving you structure in order to be able to like leaver yourself forward. o. But it looks as though this evolution of the big toe to little toe arch came about onene and a half million years before our j Gius Really? before Homo, before beforefore Homo.. Yeah. This is a key evolutionary step to how we learn to stand. Interesting hm It's good, isn't it? Yeah. Isn't that good? Here's the thing I really like about this is that this paper was published in twenty twenty Yeah Gid I ike that's like no time ago, Six years ago. Yeah, so has this been studied further, when are we going to see it folded it into what podiatrists recommend and the way shoes are designed. Great question because I think it's going to probably take quite a long time. Yeah. Because you're right that actually a lot of the time The way the shoes are designed is about thinking of the arch, thinking of the front to back arch and trying to support it and so on. But yeah, I think it probably will end up taking a lot of time. But I think it really does demonstrate just how good science is at never sitting still and continually questioning its own. This is like completely common knowledge, right? You pick up any textbook from the last seventy years or so and this is like, yeah, yeah, this is absolutely how it works. And it's not. So not only were they were these researchers willing to keep Questioning also found such a F fun but gruesome way to test it. taking cadaver feet Putting weight on it and then snipping muscles, like mutilating this foot to watch. how it how it withstands the weight and the destruction. You know the other thing you can see from the fossil record You can see the exact moment that we invented shoes. Oh, go on. Basically It's somewhere between twenty six thousand and thirty thousand years ago. So not that long ago. N that long ago. afterfter clothes, actually we were wearing clothes Okay, we were wearing clothes before shoes cles before shoes. That's almost surprising to me because I think All right, certainly You need clothing when you start migrating into colder climates. But no matter where you live, your little footseies are gonna get hurt by rocks. Well, not really, becausecause you just build up canalases on theure. I mean, that's what dogs have. I've got little dainty princess feet. and I can't even walk on sand without being like, o. But that's because I never expose them They have no chance to build up calluses. Oh right, okay. This is probably, you know, this is the combination of two together. So how do we know that shoes came about around then? Because of toes. Oh Yeah. so what happened is our toe bones, our small toe bones, especially, suddenly became really pathetic. Oh yeah. Be they were really strong and, you know amazing. So you're saying that our little tiny pinky toes, like such that sometimes the nail on it is so small you can barely paint it Because of shoes? Yeah Wow. Yeah, because they don't need to be as strong anymore when you've got the additional support. any support from the' I'm quite a big fan of walking around a barefoet. I've got to be honest. You know, like on holiday, if I could get away with it, I would just just be barefoot the whole time. Yeah. Yeah, not me. I don't sleep in socks. That's like the only time They're warm there already They're already warm enough. They get too hot. yeah. if I wear socks at night. But in the mornings I'll get up to make breakfast and I'll be walking around barefoot and I'll just be like, whoa, this is so I feel so naked. And so I don't know what my daughter thinks, because I'm always like, oh, I got to go put on socks. And she's like, why? And I'm like, Well Because I've lost my mind. a long time ago, I did. I'm still upset about something that someone said forty years ago. Yeah. I think I've seen a picture of your feet though. Can I tell you why You better do it? Do you know about I mean We said we were going to get on to foot fet. Oh, sure, yeah. Well'll come back for that after the break We live seven thousand six hundred and thirty six kilometers away from Hannah, so we rarely get to see each other in person That's what makes this such genuinely thrilling news for us and maybe for you too. because for the first time ever, you can see both of us live on stage at Goldhanger's Inaugural Festival. It's going to be amazing to be able to reach through the screen and meet those of you who watch and listen to the show in the flesh. The Rest is Fest runs from the fourth to the sixth of September at London's South Bank Center. So get some tickets and get ready for some fun. Some serious Go to southbankccenter. co. uk to find out more Let's talk about Pay Roni's disease or PD It's now widely talked about. And some men may feel reluctant to bring it up But it's more common than you'd think PD can happen when scar tissue builds up under the skin of the penis, causing a curve or a bump during an erection that for some men, may lead to pain during intimacy and impact mental health A trusted urology specialist can help diagnose PD and walk you through your options, including non surgical treatment Visit talkaboutpD. com Hey parents How do you make smarter choices for your kids' college today? That's where Sally can help With Sally, you can find scholarships, funding options, tools, and guidance all in one place And if you need a loan, Sally has options for different families and different situations College is only worth it if you do it right. So don't just help your kid go. Help them go smarter Sally d. com slash go parents Michael, do you know about Wiki feeet? I do. Do you know that you're on there Am I really? you are? Well, like I said, I did show my feet off in my Lego video Otherwise, let's do you have my Wiki Feet page bookmarked? I did look at it the other day So essentially There are a lot of people who really care a lot about feet. who find feet extremely titillating, And there is a website called WikiFeet which collects Is it called Wikieet? It was Fetipedia or something. Wikieet there they go. How does that portmanteu work? Which one do they put? one did they do? whichich collects feet ures from celebrities. and then other people can go on and write them and enjoy Enjoy looking at them. Yeah. Okay, I'm looking at the phictage of your feet right now. So you gotta show me what photos people have. I don't think these are that hairy A, Okay yeah, that's from the Lego video. Okay, so heres what here's what they have. I mean That's a normal. may have been exaggerating for ic effect. They' say this second. I want Oh yeah. when I jumped in the water. Okaykay. I don't swim in socks. there you go. I'm not some kind of like never nude foot guy. But wait a second, wait a second. What's my rating? I know I have your rating. What is it? You've done pretty well. You've done pretty well. No, hang on Let me get mine up. I wna see who wins. Oh yeah. The thing that I find extraordinary about this, apart from everything is that oh gosh, there pictures of us together online. I mean, as I say, I will wand around with our shoes on quite a lot of the time You can't even sneak into shot somewhere without ending up on this website. Exactly. Yeah. and you got to control it because that's a goldm This this is clearly worth money. Gotta gatekeep it or dollars or the ticket. Look at this. This one's gone on there Oh no. Yeah, you got some arch poking up from the shoe You know, as a guy who reads a lot of interternet comments, I know what you shouldn't be doing. I know. I'm a should be doing, depending on your goal. I do actually I mean, I do think about it now when being in front of a camera, like, okay, let's not. Right, But stop stalling. Who wins? What's our? One of us gets four point eight two. Ot of five Out five. Oh, let me guess who, who's who? I one of must guess four point eight eight. Okay well you're four point eight For sure I think four point eight two is way too high for I think it That's like that's probably only based on like two ratings. One is from like my mom twelve twelve twelve ratings. Yeah. But how many ratings do you have? How many more? more? hundredundreds? thousands? No, not thousands. Not thousands Not yet Imagine if that's the conclusion that people draw from the su. This was all just year fishing for like more ratings on Wiki feebs. It's okay if that's what you're looking to do. You know, there is a bit of me that's like, I sort of don't really have a problem with it like people having a fetish feet because they do, right? And like it's not like you're be okay with saying up andny fans a feat thing. Am I saying that? Well yeah, I mean, there's nothing, there's I would just say mayaybe you wouldn't like it because you'd rather them focus on other things about you. Yeah, true I did think about actually once saying up' and only fans, but all it is is me drawing equations on a blackboard fully clothed? Yeah, you should do that. I mean, it's only fans is for the fans and I think that's what they want. I just think it'd be really funny. Let's talk about fetishes around feet Yeah because I mean in a fetish, what is it really? it's an interest in a part of the body that is not a primarily sexual part. Yeah. Yeah, or something that is not primarily as I say, Or something. Yeah, right. So so how come foot fetishes are seemingly so much more common than like an elbow fetish or an armpit fetish. Yeah. So there is one explanation. Okay, but its there's not a lot of studies on this essentially The one explanation is that in your brain, there is effectively like a sensory map that relates to every part of your body So there's a bit in there, you know, a certain part of your brain lights up when you touch somebody's hand while they're in a scanner and so on and so on and so on And it's almost like a humunculus, right? It's like a map of your body that is in your brain.. And in that map, it has been proposed that feet and genitals are extremely close together so that you can Imagine that in some people there may be some overlap in kind of crosswiring. Right. Right. So you kind of you play around with somebody's feet and they essentially get sexual stimulation Right, right, right. So I mean, that does make a lot of sense. Yeah. But you're saying we still have a lot more to learn still have a lot more to learn because I think that the original studies or original study, rather, Ited as though it was like and there you go, that's the answer. Right. But I think subsequent follow up has demonstrated that it's just not quite as simple as that. There's much more variation that you get within humans. I mean you're right though that it is like this really prevalent thing throughout history. The Greeks and the Romans, I mean, they were really inter feat. There was one philosopher called Philo Strasus He wrotes He thought that the reason why he was so in defeat was because He wanted to be a human doormat so his lover would step on him. Okay, but then that to me becomes a second thing as well, which is dominance and submission. Yeah Yeah. I mean, it could be that that's where the whole origin of foot fetishes comes from. Maybe it does I mean, there's also the Freudian suggestion, or. Which No, what's that? Freud? see if you. As Freud generally does, it's completely unhinged. Freud says that foot fetish is because it's a trauma response to coming out of your mother's womb being first thing that you see then realizing that your mother doesn't have a penis then thinking that her feet are penis shaped, something and that you imprint on that Well look, maybe that explains my fetish for doctors because the first thing I saw when I came out of my mom was a doctor and I was like, Hey. And it was a trauma response I had because my mother's wearing, you know, wearing scrubs, like Anyway, sometimes this Freudian stuff, it's like like a fantasy. It's hilarious. And I think useful in the same way that like Fantasy novels are useful and they can be so so inspiring, but I'm just like, I don't know how any of this is scientific. It's no. I mean, some of it, I guess can be, but some of it I'm like, wow, this is really creative. Well, it's not false fireboy, is it? It's just not false fireball. No.l unless you I don't know, like do a controlled trial where you get half of all women to wear socks while giving birth Yeah, exactly. And then you check the future fedations of those babies and they're like, oh, I don't know. But see, they might just wind up being really into sock feet The thing is that when it comes to fetishes, you can learn a fetish though. Oh So there's an amazing study with rats. Okay, tellell me about it. Can I tell you? Okay. so what they did, they wanted to see if they could give rats a fetish I love this. ye. They took virgin male rats and they gave a little put a little jacket on them Kilo jacket. Okay. and some of the jacketed rats put in with females and then they all had a lovely time. They were This is brilliant. These jackets are great And then the others, when they put on the jacket they were They were introduced to females, but they were not allowed to copulate. okay. So they were like right, so this is like a The jacket is a cock block. Right, essentially. Right. And so they sort of did that a few times and then for the final test They took the jackets off of everybody of all of them rs The rats who had learned that the jacket meant good times, okay They then didn't know what to do when they weren't wearing the jacket. Becauseuse they had like so closely associated the jacket. They were just like, I can't no, thank you, I can't get off without my jacket. Any of my jackets are in this. vice versa, the ones who had learned that the jacket meant disisappointment. Yeah. When the jacket went on, They were like, No, thank you. I'm not interested. can't do it. can't do it when I'm wearing this. Yeah. So it's like there is something some evidence that this is learned. There's some learning and some associations. Yeah. I mean, I don't find that surprising at all. think You know, as you get to know someone better and you have all these experiences together, the roots of your trees grow closer and you start to just love things about them, physical things about them that you find so much more exciting than you used to Um, because I don't know. it's them. it's it's theirs and you love them So like I find myself I don't personal Like basically I just Basically As I get older, find my wife more attractive. Oh, that's a lovely thing to say. And I'm not just saying that for like points or anything I'm saying it because I've heard comedians, like old comedians make jokes about this too And I'm like, yeah, that really is true. Right. That's lovely. That's lovely, but it's like the learned It's a lear being with her and around her. And then what's the difference between just admiration? Like, oh, your hair is so wonderful and a fetish. I don't know, is the jacket on or off? Thats. Right. And just how much do I want that jacket on Do I think it's a nice jacket or do I think it's a nice jackt? Right. It's probably there's a g spectrum. Somewhere between. You gott to decide every day where you are between those two endpoints. I do, I do. Well what I'm looking forward to is my Cambridge colleagues listening to this podcast and the first half being like, Well, that's really hard. I'm very interested in segreation Sorry, what are you talking about rat fetishes? Well no, I'm glad someone studied that. because it's good, isn't it? I would be embarrassed to like be like, I need money to do this study. Do you want to see the jacket? Yeah Oh wow, that is so not sexy. It's not sexy, is it? But some of the rats thought it was Some of the rats learned someome of the rats thought it was. And some people think feet are. and some people like nostrils. you know? and I think The world needs all those kinds of appreciation. Absolutely. And we appreciate you. We certainly do. Thank you for listening and reach out to us, ask us questions at the rest is science at goalhanger d. comot and we will see you next time. Thank you time